Execute.OnBackgroundThread in Caliburn.Micro

We're currently exploring options to potentially move from Caliburn to CM. I noticed the Execute.OnBackgroundThread() no longer exists in CM - what was the reasoning behind this, and is there an alternative available (other than to just explicitly
create a new thread)?

It was mainly removed to keep things small and to simplify the core and its dependencies. There isn't any alternate version available in the framework. YOu might consider just using the Task APIs instead. (That's what I do.)